The present invention relates to wireless communication systems in general, and particularly relates to managing connections between a radio network and an access terminal.
Wireless communication services are, for many people, an integral part of everyday life. Beyond the convenience and safety afforded by voice communication services, an increasing number of users expect their wireless devices and supporting radio networks to provide ready, useful access to an increasingly rich array of information services. Wireless connection with the Internet illustrates a primary example of the trend toward providing a broad range of increasingly sophisticated communication services.
In general, 1st and 2nd generation radio networks were designed primarily to handle voice communications. These networks have been adapted to handle some data communications, such as fax communications, but are not particularly suited to handle packet data. Therefore, new radio communication protocols specifically adapted to handle packet data communications have evolved and are currently being implemented. Some of these new communication protocols, such as IS-2000, are capable of both voice and data communication. Other communication protocols being developed, such as the General Packet Radio Service (GPRS) and IS-856 standard are intended to handle packet data traffic, but not voice traffic. One advantage of dedicated packet data networks is that they are capable of relatively high data rates as compared to radio networks that handle both voice and packet data.
Since packet data services are popular among consumers and business users, many access terminal manufacturers offer dual mode access terminals that can communicate with both voice networks, such as an IS-95 or IS-2000 radio network, and packet data networks, such as an IS-856 network. Thus, a user can use the same access terminal to establish a connection with a packet data network to browse the Internet, or to connect with a voice network to place a voice call. In the very near future, dual mode access terminals will be able to handle simultaneous voice and data connections.
Incompatible standards employed by packet data and voice networks pose a problem for dual mode access terminals. For example, the packet data network may employ a different communication protocol than the voice network. In some cases, the different communication protocols used by the different radio networks prevent sharing information between radio networks or interworking to facilitate dual mode operation. Thus, the access terminal must carry the burden of maintaining communications with two incompatible radio networks. In these circumstances the access terminal must comply with the communication protocols of both radio networks.
This inter-network incompatibility poses certain connection management challenges when an access terminal maintains communication with two or more incompatible radio networks. Assume, for example, that the access terminal is capable of dual mode operation in an IS-856 network and an IS-2000 network. In the IS-856 network, the access terminal is expected to transmit continuously on the reverse traffic channel (RTC), monitor the forward control channel, and demodulate the reverse link power control (RPC) channel, while its connection to the radio network is open. At the same time, the access terminal must be able to receive page requests that are sent from the Mobile Switching Center (MSC) via the IS-2000 radio network while maintaining its connection with the IS-856 radio network. Such page requests may be intended for voice call delivery or Short Message Service (SMS) delivery, or delivery of other services. The access terminal must also be able to perform certain procedures required by the IS-2000 radio network, such as idle hand-off procedure, registration procedures, as well as many other idle state procedures.
In the current state of the art, an access terminal with an active connection on the IS-856 radio network temporarily suspends communication with the IS-856 radio network to monitor the paging channel and detect incoming pages in the IS-2000 network, if any, and to perform idle hand-offs, registration, or other idle state procedures if necessary. When the access terminal is finished monitoring the paging channel and performing other idle state procedures, it then resumes communication with the IS-856 radio network by resuming its transmission on the RTC and its monitoring of the forward control channel.
When the access terminal ceases communication with IS-856 radio network to monitor the paging channel on the IS-2000 radio network or to perform other idle state procedures, the IS-856 radio network initiates a fade timer. If the access terminal does not resume communications before the expiration of the fade timer, the IS-856 radio network may terminate the access terminal's connection and release resources associated with that connection. Those resources include the traffic channels assigned to the access terminal and the RPC channel that is used by the serving base station for closed loop reverse link power control. The access terminal may be unaware that its connection with the IS-856 radio network was terminated.
Problems may arise if the access terminal attempts to resume communication on the IS-856 radio network after its connection has been terminated. If the access terminal subsequently resumes communication unaware that resources needed for RTC demodulation have been de-allocated, its transmission on the RTC will appear as noise to the radio network increasing the level of interference at the base station receiver. Further, if an access terminal returning from suspended communication fails to recognize that its previously allocated RPC channel has been reassigned to a second access terminal, it may erroneously respond to power control commands intended for the second access terminal. In some circumstances, the interfering access terminal could increase its transmit power to the point that the base station receiver is desensitized, which may cause other active access terminals to also increase their transmit power, which may further desensitize the base station receiver. If the level of desensitization exceeds a certain limit, the base station receiver may suffer a reverse link outage, which in extreme circumstances may lead to a complete service disruption.